Jim, If he has the HPOP out, he should be able to identify the anti-drain back check valve from the 94-95 model trucks... I have attached a picture. if that isn't there, its a later year HPOP. Hope that helps.
2000 F350 CCLB 4x4 auto, 250/200's from PIS, No Limit tunes, Isspro gauges, 4" exhaust and intake.